Manufacture of semiconductor components requires the selective doping of predetermined zones or regions of a body of semiconductor material. Diodes of various types, for example solar cells, transistors, integrated circuits and other semiconductor elements can be made by ion implantation. This method has become increasingly important in recent times.
An extraordinary variety of doping problems can be solved when using ion implantation in monocrystalline semiconductor material. Variations of process parameters, such as the energies of ions being implanted, the types or species of ions, the doses, the beam geometry, and the like, can be used to vary the results to be obtained.
Doping of amorphous semiconductor material has not been satisfactory heretofore since it has been impossible to achieve sufficient electrical activation of the implanted ions as donors or acceptors in the hose material. No technically useful conductivity changes could be obtained by the ion implantation process when used with amorphous semiconductor materials. It was, therefore, believed that ion implantation methods to dope amorphous semiconductor materials is not a technically suitable process. Ion implantation has been carried out at room temperature--approximately 20.degree. C.--and much below this temperature; the referenced publication by Rehm et al., for example, notes that the effect of phosphorus ion implantation in amorphous silicon at a temperature of 80.degree. K. disappeared after annealing of the semiconductor silicon body at about 200.degree. C. It was inferred that the originally observed change in conductivity was based principally on the radiation effects. Amorphous germanium which, in its properties, is closely related to or resembles silicon, has been used as a basis for ion implantation--see the referenced article by Anderson et al. Implantation of boron ions was attempted and it was noted that the increase in conductivity was at most by a factor of 40 without, however, significant displacement of the Fermi level.